Electron transitions during the capture of an electron by a He$^{2+}$ ion at the argon atom

We have measured the absolute values of the total cross section of the one-electron capture by He$^{2+}$ ions in the kinetic energy range 2–30 keV at the Ar atoms. The absolute values of the differential scattering cross sections of He$^+$ ions formed during the one-electron capture and the electron capture with ionization at energies of 2.2, 5.4, and 30 keV have been determined. The electronic states of the formed ions have been determined using collision spectroscopy based on analysis of the change in the kinetic energy of He$^+$ after the interaction. We have measured doubly differential (with respect to the kinetic energy and the scattering angle) cross sections of the formation of free electrons. The free electron formation channels (direct ionization and electron capture with ionization) have been analyzed by calculating the electron terms of the (HeAr)$^{2+}$ system. The calculated cross section of capture with ionization is in conformity with the cross section measured using collision spectroscopy.